Researches On The Algorithms Of GNSS Triple Frequency Precise Positioning

Future global navigation satellite system (GNSS), such as the US Modernized global positioning system (GPS), the European Galileo system and the Chinese COMPASS system, will all operate with three or more frequencies, which bring great benefit to precise positioning. This dissertation lays emphasis on the study of the theory of triple-frequency combination observations, cycle-slips detection and repair, and three carrier ambiguity resolution. The main achievements of this paper are listed as follows:1. The theory of triple-frequency combination observations is investigated profoundly, and a method to solve the optimal integer coefficients of combination observations is developed based on three integer linear transforms from three integer coefficients of combination observations to the wavelength factor, ionosphere amplification factor and the sum of the integer coefficients of these combinations. It is proved that the sum of three integer coefficients of extra-wide-lane or wide-lane combinations with long wavelength, low amplification factor for ionosphere and low noise should equal to zero, and the sum of three integer coefficients of narrow-lane combinations with small ionosphere effect and low noise should equal to one. It is also proved that the ionosphere amplification factor of extra-wide-lane or wide-lane combinations with long wavelength and low noise increased when the sum of the integer coefficients increased, and the ionosphere amplification factor is about 12 times of the sum of the integer coefficients.2. The error characteristics of common combinations with real coefficients are analyzed, and the method to resolve the optimal coefficients of these combinations is given.3. The methods of cycle-slips detection and repair based on triple-frequency combination observations are researched, and the threshold for detecting cycle-slips based on pseudo-range/phase combinations is deduced. From the purpose of improving the success rate of cycle-slips determination, the criterion and method of selecting the optimal combinations are given. The ability of real-time cycle-slips repair is analyzed. The results show that cycle-slips can be repaired when the change of ionosphere delay between epochs can be ignored, even though under condition of 3 meters standard deviation of pseudo-range. However, considering variation of ionosphere delay between epochs, cycle-slips can not be repaired even though the standard deviation of pseudo-range is 0.3 meters.4. The error influence factors of Cascading Integer Resolution method for double or triple frequency carrier observations are analyzed. It shows that low success rate of wide-lane ambiguity resolution in first step is the main cause of low success rate of ambiguity resolution by Cascading Integer Resolution method for double frequency carrier observations in single epoch in the condition of short baseline. Thanks to the addition of extra-wide-lane combination in the Cascading Integer Resolution method for triple frequency observations, the success rate of wide-lane ambiguity resolution in single epoch is improved so that this method can be used for instantaneous ambiguity resolution in the condition of short baseline.5. Aiming at the rapid resolution of narrow-lane ambiguity for median-long baseline, a method based on decomposition of ambiguity with triple frequency geometry-free and ionosphere-free observation combination is proposed. A scheme for ambiguity resolution without geometry and ionosphere delay influence in the condition of long baseline is given and rapid resolution is implemented.6. Influence of double-difference troposphere delay residual to GNSS positioning accuracy is analyzed. The result shows that considering the zenith troposphere delay parameter will decrease the positioning accuracy in the condition of short baseline and low height difference, but it will improve height component solution accuracy evidently in case of great height difference.